Obion, Tennessee, United States [County]; population was 31,717 in 1990; housing units was 13,359 in 1990; location is 36°22'N 89°9'W; land area is 544.95 square miles (348,769 acres); water area is 10.43 square miles (6,676 acres); FIPS code is 131 [SourceCBP]